i would go and take my childs own food. did that for many years, until my family 'got it'
must confess that i used a newspaper clipping to ram our situation home to every one. a article of someone who died from a nut allergy. i gave it to them to skim over , and added, that our boy had many many more allergies than just peanut allergy, and all could 'take him away' if he wasnt careful.
my son was very young at the time, and i was fed up with having to stress every time we got together about food. fed up of hearing the 'oh, just give him a little bit, it will build up his resistance'
i never expected them to really understand instantly, as they dont live with it,
but wanted to get across that as a young kid, just not giving him the food, but giving it to other kids in the room was not a safe environment for him.
over the years, everyone made sure, without me having to phone, that everything was safe. if they had a problem , they rang to ask, and i would bring something.
so, my advice is to be patient, you might get some support in the end. although, i have to say, my family may not of understood my stress, but because of repeated reactions to new stuff, hosptial visits over the years, they understand now!
hhowever dont let them put your child at risk, they dont undestand, you do, and you are the barrier that protects your child until they are old enough to cope on their own.
and , if you have to sadly conclude that they are always going to be dangerous around your kids, stop seeing them, until your kids is older.